Chapter 1501:21-13 Classification and Design of Dams, Dikes, and Levees

(A)
For the purpose
of this chapter, dams shall be divided into four classes, which shall be known
as class I, class II, class III, and class IV. The chief shall establish a
dam's appropriate classification by using the following criteria as a
guideline. Such classification shall be established by the chief during the
preliminary review described by rule
1501:21-5-02 of the
Administrative Code or during the periodic inspection described by rule
1501:21-21-01 of the
Administrative Code. The chief reserves the right to reclassify any dam at any
time as a result of circumstances not in existence or not known at the time
said dam was initially classified.

(1)
Dams
having a total storage volume greater than five thousand acre-feet or a height
of greater than sixty feet shall be placed in class I. A dam shall be placed in
class I when sudden failure of the dam would result in one of the following
conditions.

(b)
Structural collapse of at
least one residence or one commercial or industrial business.

(2)
Dams having a total storage
volume greater than five hundred acre-feet or a height of greater than forty
feet shall be placed in class II. A dam shall be placed in class II when sudden
failure of the dam would result in at least one of the following conditions,
but loss of human life is not probable.

(a)
Disruption of a public water supply or wastewater treatment facility, release
of health hazardous industrial or commercial waste, or other health hazards.

(b)
Flooding of residential,
commercial, industrial, or publicly owned structures. At the request of the dam owner, the chief may exempt dams
from the criterion of this paragraph if the dam owner owns the potentially
affected property.

(c)
Flooding of high-value property. At the request of the
dam owner, the chief may exempt dams from the criterion of this paragraph if
the dam owner owns the potentially affected property.

(d)
Damage or disruption to major roads
including but not limited to interstate and state highways, and the only access
to residential or other critical areas such as hospitals, nursing homes, or
correctional facilities as determined by the chief.

(f)
Damage to
downstream class I, II or III dams or levees, or other dams or levees of high
value. Damage to dams or levees can include, but is not limited to, overtopping
of the structure. At the request of the dam owner, the
chief may exempt dams from the criterion of this paragraph if the dam owner
owns the potentially affected property.

(3)
Dams having a total storage volume
greater than fifty acre-feet or a height of greater than twenty-five feet shall
be placed in class III. A dam shall be placed in class III when sudden failure
of the dam would result in at least one of the following conditions, but loss
of human life is not probable.

(a)
Property
losses including but not limited to rural buildings not otherwise described in
paragraph (A) of this rule, and class IV dams and levees not otherwise listed
as high-value property in paragraph (A) of this rule. At the request of the dam
owner, the chief may exempt dams from the criterion of this paragraph if the
dam owner owns the potentially affected property.

(b)
Damage or disruption to local roads
including but not limited to roads not otherwise listed as major roads in
paragraph (A) of this rule.

(4)
Dams which are twenty-five feet or less
in height and have a total storage volume of fifty acre-feet or less may be
placed in class IV. When sudden failure of the dam would result in property
losses restricted mainly to the dam and rural lands, and loss of human life is
not probable, the dam may be placed in class IV. Class IV dams are exempt from
the permit requirements of section
1521.06 of the Revised Code
pursuant to paragraph (C) of rule
1501:21-19-01 of the
Administrative Code.

(B)
All pertinent information including any
unusual circumstances shall be considered by the chief in establishing an
appropriate classification for a dam. Probable future development of the area
downstream from the dam that would be affected by its failure shall be
considered. Completed downstream hazard mitigation such as acquisition, removal
or protection of downstream property may also be considered. However, the above
criteria shall in no way preclude the chief's requirement of greater safety in
the interest of life, health, or property.

The magnitude of the design flood for each dam shall be set by
the chief and determined from actual streamflow and flood frequency records or
from synthetic hydrologic criteria based on current publications prepared by
the division, the United States army corps of engineers, the United States
geological survey, the national oceanic and atmospheric administration, or
others acceptable to the chief.

(3)
For class III dams, twenty-five percent
of the probable maximum flood or the critical flood.

(B)
Selection of a critical flood as the
design flood is acceptable. The design for the critical flood shall be for
site-specific conditions and based on a quantitative and relative impact
analysis of the downstream critical routing reach. In determining the critical
flood, the spillway and storage capacity for the dam shall be designed so that
there will be no additional potential for loss of life, health or property in
the critical routing reach from overtopping failure of the dam when compared to
the potential for loss of life, health or property caused by the flood in the
absence of a dam overtopping failure.

(1)
Where the incremental depth of flow between the failure and non-failure floods
is 2.0 feet or greater, or the product of the average floodplain flow velocity
(in feet per second) and the incremental flood depth (in feet) is greater than
7.0, additional potential for loss of life, health or property in the critical
routing reach is expected.

(2)
If
the incremental depth of flow between the failure and non-failure floods is
less than 2.0 feet, and the product of the average floodplain flow velocity (in
feet per second) and the incremental flood depth (in feet) is less than 7.0, it
does not necessarily mean that the critical flood has been determined. Further
investigation will be required to determine that no additional potential for
loss of life, health or property will occur.

(D)
The owner or applicant shall submit to
the chief, in writing, a request for consideration of the critical flood as the
design flood. This request shall be accompanied by appropriate supporting
calculations. The chief will not consider risk assessment based upon planned
evacuation, probability of inhabitation, or monetary recovery of property
damage.

(E)
If downstream hazard
conditions change at any time during the life of the structure, a reevaluation
of the critical routing reach and modification of the critical flood may be
required by the chief.

(A)
Every dam shall have a spillway system
which will safely operate during the design flood without endangering the
safety of the dam.

(B)
Each
spillway shall include a means of dissipating the energy of flow without
endangering the safety of the dam.

(C)
The capacity of the spillway system shall
be equal to the peak inflow rate of the design flood unless the applicant has
demonstrated by flood routing procedures that the dam will safely pass the
design flood with the spillway system.

(D)
Every upground reservoir shall have an
overflow or other device to preclude overfilling the reservoir during normal
filling operations. Local watershed drainage into the reservoir must also be
included in the design of the overflow device if applicable.

(1)
The elevation of an overflow device shall
be no more than 0.5 foot above the designed maximum operating pool level of the
reservoir.

(2)
A device other than
an overflow that is used to preclude overfilling must prevent the reservoir
from rising 0.5 foot above the designed maximum operating pool level.

(A)
All pipe conduits shall convey flow at
the maximum design velocity without damage to the interior surface.

(B)
Seepage control devices acceptable to the
chief shall be installed. .

(C)
Adequate allowances shall be incorporated in the design to compensate for
settlement and possible elongation of the pipe conduit.

(D)
An anti-vortex device that is
satisfactory to the chief shall be installed at the intake of all pipe and
riser spillway systems. Anti-vortex devices may also be required for other
spillway types as necessary to improve the performance of the spillway.

(E)
A trash rack that is
satisfactory to the chief shall be installed at the intake of all pipe and
riser and/or drop inlet type spillway systems to prevent clogging the pipe
conduit. Trash rack devices may also be required for other spillway types as
necessary to ensure the performance of the spillway.

(F)
An emergency overflow spillway shall be
required, except when specifically exempted by the chief. A vegetated or
unlined emergency spillway will be approved by the chief, but only after the
applicant has demonstrated that it will pass the design flood without
jeopardizing the safety of the structure. The average frequency of use for a
vegetated or unlined emergency spillway must be predicted to be less than the
following criteria unless otherwise approved by the chief:

(G)
The pipe conduit shall be of such size as
to remove from the reservoir within ten days following passage of the design
flood peak at least eighty percent of the water temporarily detained in the
reservoir above the elevation of the primary (principal) spillway.

(A)
Dams in class I, class II, and class III
shall include a device to permit draining the reservoir within a reasonable
period of time as approved by the chief. Pipe conduits used for lake drains
shall have a minimum inside diameter of not less than four inches.

(B)
Valves or sluice gates in pipe conduits
shall be installed upstream from the centerline of the dam unless otherwise
approved by the chief.

(C)
All
pipe conduits used as drains, water supply lines, or other pressure-flow
conduits, regardless of classification of the dam, shall meet the requirements
of paragraphs (A), (B), (C), and (E) of rule
1501:21-13-04 of the
Administrative Code and paragraphs (A), (C), and (D) of rule
1501:21-13-05 of the
Administrative Code.

(D)
When the
drain outlets into a pipe-conduit upstream from the centerline of the dam,
seepage control devices may be omitted from the drain.

(E)
All new dam
construction shall include a bulkhead for the outlet works unless specifically
exempted by the chief.

Sufficient freeboard shall be provided to prevent overtopping
of the top of the dam due to passage of the design flood and other factors
including, but not limited to, ice and wave action. The chief may approve a
lower freeboard requirement if the dam is armored against overtopping erosion.

(A)
For class I and class II dams
that are upground reservoirs, the minimum elevation of the top of the dam shall
be at least five feet higher than the elevation of the designed maximum
operating pool level unless otherwise approved by the chief.

(B)
For class III dams that are upground
reservoirs, the minimum elevation of the top of the dam shall be at least three
feet higher than the elevation of the designed maximum operating pool level
unless otherwise approved by the chief.

(A)
The safety factors for the various
elements of the dam shall conform to good engineering practice as approved by
the chief. The safety factors and the design standards that are used by the
applicant shall agree with the approved design assumptions.

(B)
Inspection devices such as piezometers,
settlement platforms, stand-pipes, tell-tale stakes, monitoring weirs,
inclinometers, and permanent bench marks, may be required by the chief for the
division's and the owner's use in the inspection of the structure during and
after completion of construction.

(C)
The chief may
require dams to have a staff gauge to allow monitoring of lake levels within a
range from the lower of five feet below normal pool or the normal drawdown
level, to the top of dam elevation. The design of the staff gauge will be
reviewed and approved by the chief.

(D)
Grass vegetation or other vegetation of similar
properties are the only acceptable vegetative covers for earthen dam embankment
surfaces or vegetated earth spillways. Trees and brush are not acceptable
surface covers.

(E)
The applicant shall
demonstrate to the satisfaction of the chief that the structure will be
consistent and in accordance with all applicable state and local floodplain
regulations and requirements.

(A)
For the
purpose of this chapter, levees shall be divided into four classes, which shall
be known as class I, class II, class III, and class IV. The chief shall
establish a levee's appropriate classification by using use the following
criteria as a guideline. Such classification shall be established by the chief
during the review of the preliminary design report described by rule
1501:21-5-02 of the
Administrative Code or during the periodic inspection described by rule
1501:21-21-01 of the
Administrative Code. The chief reserves the right to reclassify any levee at
any time as a result of circumstances not in existence or not known at the time
said levee was initially classified.

(1)
A
levee shall be placed in class I when sudden failure of the levee would result
in one of the following conditions.

(d)
Damage or disruption to major
roads including but not limited to interstate and state highways, and the only
access to residential or other critical areas such as hospitals, nursing homes,
or correctional facilities as determined by the chief.

(3)
A
levee shall be placed in class III when sudden failure of the levee would
result in at least one of the following conditions, but loss of human life is
not probable.

(a)
Property losses including
but not limited to rural buildings not otherwise described in paragraph (A) of
this rule.

(b)
Damage or
disruption to local roads including but not limited to roads not otherwise
listed as major roads in paragraph (A) of this rule.

(4)
A levee having a height of not more than
three feet shall be placed in class IV. When sudden failure of the levee would
result in property losses restricted mainly to the levee and to the owner's
property or to rural lands, and loss of human life is not probable, the levee
may be placed in class IV. Class IV levees are exempt from the permit
requirements of section
1521.06 of the Revised Code
pursuant to paragraph (C) of rule
1501:21-19-01 of the
Administrative Code.

(B)
All pertinent information including any
unusual circumstances shall be considered by the chief in establishing an
appropriate classification for a levee. Probable future development of the area
adjacent to the levee shall be considered. However, the above criteria shall in
no way preclude the chiefs requirement of greater safety in the interest of
life, health, and property.

(A)
Future development of areas upstream,
downstream, and adjacent to the levee shall be considered in the design.

(B)
The levee shall operate safely
during all floods up to the design flood elevation.

(C)
Provisions for drainage of the area
protected by the levee shall be incorporated into the structure. Measures shall
be included to prevent flooding of this area by backflow through the drainage
system.

(D)
The levee must be
protected from or designed to prevent erosive velocities along the structure
and its foundation.

(E)
Grass
vegetation or other vegetation of similar properties are the only acceptable
vegetative covers for earthen levee embankment surfaces. Vetch, trees and brush
are not acceptable surface covers.

(A)
Hydraulic analyses shall be conducted to
determine flood elevations for stream reaches affected by the construction of a
levee and in accordance with rule
1501:21-13-10 of the
Administrative Code. The analyses must provide flood depth and velocity data
during the one-hundred-year, twenty-five-year, and five-year flood events, and
for the top-of-levee flood event. For construction of new levees, the flood
depths and velocities must be determined with and without the levee. The impact
of increased flood depths and velocities on property and structures must be
provided.

(A)
The
design flood shall be established by the chief in concert with the applicant's
desired level of protection, but with the utmost interest in safeguarding life,
health, and property. For class I levees, the minimum design flood will be the
one-hundred-year flood or the critical flood. The design for the critical flood
shall be for site-specific conditions and based on a quantitative and relative
impact analysis of the protected area. In determining the critical flood, the
levee shall be designed so that there will be no additional potential for loss
of life, health or property from overtopping failure of the levee when compared
to the potential for loss of life, health or property caused by the flood in
the absence of a levee overtopping failure.

(B)
The magnitude of the design flood shall
be determined from actual streamflow and flood frequency records or from
synthetic hydrologic criteria based on current publications prepared by the
division, the national oceanic and atmospheric administration (NOAA), the
United States army corps of engineers, the United States geological survey, or
others specifically approved by the chief.

(A)
For levees in class I, the minimum
elevations of the top of the levee shall be at least three feet higher than the
maximum adjacent water surface elevations during passage of the design flood.
The chief may approve a lower freeboard requirement
with acceptable documentation.

(B)
For levees in class II and class III, the
minimum elevations of the top of the levee shall be two feet higher than the
maximum adjacent water surface elevations during passage of the design flood.

(C)
Where special conditions of
severe frost damage, ice damage, stream obstruction, wave action, or impact of
other structures may occur, the chief may require elevations higher than
required in paragraph (A) of this rule.

(A)
The safety factors of the various
elements of the levee shall conform to good engineering practice as approved by
the chief. The safety factors and the design standards that are used by the
applicant shall agree with the approved design assumptions.

(B)
Design references that are used shall be
cited in the information that is submitted to the chief.

(C)
Inspection devices, which include but are
not necessarily restricted to settlement platforms, tell-tale stakes,
inclinometers and permanent bench marks, may be required by the chief for the
division's and the owner's use in the inspection during and after completion of
construction.